DESCRIPTION(adapted from applicant's abstract): The long-term goal of the proposed research is to identify and understand the cellular mechanisms of spatial attention. Previous accounts of the mechanisms underlying spatial attention are based on damage to structures following strokes in human patients. However, the results of these studies neither correlate well with each other nor with monkey studies that used more precise, reversible lesions of the same structures, despite the interspecies similarity of attention shifting behaviors. Our goal is to develop a model of attention shifting that is more consonant with new data on 1) the mechanisms that move the eyes, 2) the interdependence of structures mediating overt and covert movements in humans, and 3) new data on the importance of acetylcholine for covert orienting. To accomplish this, we will use the method of iocal drug infusion to alter attentional orienting in trained Rhesus monkeys. The animals are taught to shift attention to peripheral targets while maintaining visual fixation. As a control condition, they are also tained to attend to target changes at the fixation point. The results will be important because they will identify the structures normally used to shift the attention, and by deduction, the structures that are malfunctioning in attention-deficit disorder and Alzheimer's disease. The pharmacological results may also help develop more rational strategies for treating attentional disorders and may clarify the attentional benefits of tobacco use and abuse.